CN110665987A

CN110665987A - Extrusion forming die of magnesium alloy bar without anisotropy

Info

Publication number: CN110665987A
Application number: CN201910965827.9A
Authority: CN
Inventors: 张治民; 贾蕾琛; 吴国琴; 张慧芳; 郝红元; 于建民
Original assignee: North University of China
Current assignee: North University of China
Priority date: 2019-10-12
Filing date: 2019-10-12
Publication date: 2020-01-10
Anticipated expiration: 2039-10-12
Also published as: CN110665987B

Abstract

The invention discloses an extrusion forming die for a magnesium alloy bar without anisotropy, which comprises an insert, a male die and a female die, wherein the male die is connected with a press machine to axially move, the female die is connected with a rotating mechanism to circumferentially rotate, a die cavity is arranged in the female die, the die cavity is provided with a feeding port, an extrusion working belt is also arranged in the die cavity, the feeding port is used for placing the insert, the bar and the male die, and the insert is arranged at the extrusion working belt. The invention applies torque on the basis of the traditional extrusion, can increase the revolution number of rotation by changing the rotation speed, improve the gradient structure generated under the rotary forming, realize the uniform deformation of the structure, generate larger shearing strain quantity by changing the internal stress strain state of a deformation body, can refine crystal grains, form a fine crystal structure with large-angle grain boundaries, and reduce the anisotropy of a component.

Description

Extrusion forming die of magnesium alloy bar without anisotropy

Technical Field

The invention belongs to the technical field of metal plastic processing technology and forming, and particularly relates to an extrusion forming die for a magnesium alloy bar without anisotropy.

Background

Extrusion is widely used in the field of plastic forming of metal materials due to its advantages of high efficiency, high quality and low consumption. The traditional extrusion processing mode refers to: and applying external force to the metal bar placed in the die cavity to force the metal to be extruded out of the die hole, so as to obtain a workpiece with a required section shape and size and certain mechanical property. The bar stock during the positive extrusion deformation is roughly divided into: a deformation zone, an undeformed zone, and a dead zone. In the deformation zone, the metal flow is not uniform, the central layer flows fast, and the outer layer flows slowly; the degree of non-uniform deformation is the same after entering the stable deformation phase. Metal "dead zones" of varying degrees may be created at the die exit corners. Due to the fact that stress and strain states of all deformation regions are different in the forward extrusion process, deformation amounts of different regions are different, deformation is extremely uneven, and strong basal plane textures are easily formed in the extrusion process, so that strong anisotropy is shown. When the metal is in a three-dimensional compressive stress state during extrusion, although the plasticity of the metal is improved, due to the existence of additional stress, cracks are often generated during extrusion of low-plasticity materials, so that products are scrapped, and the application universality of the extrusion process is restricted.

Disclosure of Invention

The invention aims to provide an extrusion forming die of a magnesium alloy bar without anisotropy, which obviously reduces axial extrusion force, eliminates extrusion deformation texture, reduces anisotropy, enables a formed piece to deform more uniformly, greatly improves the mechanical property of a formed workpiece and improves the material utilization rate.

In order to achieve the purpose, the technical scheme of the invention is as follows:

the extrusion forming die comprises an insert, a male die connected with a press machine and a female die connected with a rotating mechanism, wherein the male die is connected with the press machine to axially move, the female die is connected with the rotating mechanism to circumferentially rotate, a cavity is arranged in the female die, the cavity is provided with a feeding port, an extrusion working belt is further arranged in the cavity, the feeding port is used for placing the insert, a bar and the male die, and the insert is arranged at the extrusion working belt.

Preferably, the punch is arranged at the tail end of the male die, the punch is placed into the material inlet to extrude the bar, the bottom surface of the punch is provided with a limiting groove, the end surface of the bar, which is in contact with the bottom surface of the punch, deforms along with extrusion to generate a limiting block matched with the limiting groove, and the limiting block is embedded into the limiting groove to enable the male die to limit the bar to rotate along with the rotation of the female die.

Preferably, the extruding working belt forms a clamping block, the insert forms a clamping groove at a position corresponding to the clamping block, and when the insert is placed into the extruding working belt from the feeding port, the insert is mounted at the extruding working belt through the matching of the clamping groove and the clamping block.

Preferably, the insert is uniformly distributed with a plurality of inclined grooves along the circumferential direction, and the inclined grooves are grooves which deflect around the central axis of the insert.

Preferably, the die further comprises an ejection mechanism for discharging the formed bar stock.

Compared with the traditional forward extrusion method, the invention has the advantages that:

(1) after the torque is added to the female die, the stress state of each deformation area is changed in the forward extrusion process, particularly the stress strain state of the hard deformation area and the deformation area is changed, and the deformation uniformity is improved;

(2) the bar metal passing through the extrusion working belt flows along the loaded axial direction, and the torsional deformation generated along the circumferential direction is increased, and the torsional deformation can be changed along with the increase of the rotating speed and the rotating number of the revolutions, so that the bar with high mechanical property can be obtained when the extrusion is relatively small;

(3) under the same structure condition, the forming load and the tonnage of equipment can be reduced, thereby realizing the purpose of 'small equipment dry and big activity';

(4) by adopting the insert structure, under the condition that the male die and the female die are not changed, the extrusion ratio can be changed by replacing forming parts, the deformation degree of materials is changed, the purpose of forming various types of bars by one set of die is realized, and the production cost is greatly reduced. The invention increases the active shear stress in the extrusion process, reduces the material forming flow stress, refines the crystal grains, eliminates the extrusion deformation texture and realizes the extrusion forming of the uniform bar without anisotropy. Meanwhile, the insert structure is adopted, so that the wear-resistant die is convenient to replace in time, the service life of the die is prolonged, and the economic benefit is remarkable when the die is popularized in the forging industry.

Drawings

FIG. 1 is a schematic structural view of a male mold according to an embodiment of the present invention;

FIG. 2 is a bottom view of the punch of FIG. 1;

FIG. 3 is a side view of the punch of FIG. 1;

FIG. 4 is a schematic structural diagram of a female mold according to an embodiment of the present invention;

FIG. 5 is a top view of a female mold in accordance with one embodiment of the invention;

FIG. 6 is a top view of an insert according to an embodiment of the present invention;

FIG. 7 is a cross-sectional view taken along A-A of FIG. 6;

FIG. 8 is a bottom view of an insert according to an embodiment of the present invention;

FIG. 9 is a schematic view of a mold assembly according to one embodiment of the present invention;

fig. 10 is a schematic diagram of an operation process according to an embodiment of the present invention.

Description of reference numerals:

1-insert block, 11-clamping groove, 12-inclined groove, 2-convex die, 21-punch head, 22-limiting groove, 3-concave die, 31-die cavity, 311-feeding port, 312-extrusion working band, 3121-clamping block and 4-bar material.

Detailed Description

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts, please refer to fig. 1-10.

An extrusion forming die for a magnesium alloy bar without anisotropy please refer to fig. 1, fig. 2, fig. 7 and fig. 9, which comprises an insert 1, a male die 2 connected with a press (not shown in the figure), a female die 3 connected with a rotating mechanism (not shown in the figure) and an ejection mechanism (not shown in the figure), wherein the male die 2 is connected with the press to move axially, the female die 3 is connected with the rotating mechanism to move circumferentially and rotatably, a die cavity 31 is arranged in the female die 3, the die cavity 31 is provided with a feeding port 311, an extrusion working belt 312 is also arranged in the die cavity 31, and the feeding port 311 is used for placing the insert 1, the bar 4 and the male die 2.

As shown in fig. 1 to 3, the end of the male die 2 is a punch 21, the punch 21 is inserted into the material inlet 311 and extrudes the rod 4, the bottom surface of the punch 21 is provided with a limit groove 22, the end surface of the rod 4 contacting with the bottom surface of the punch 21 generates a limit block (not shown in the figure) matching the shape of the limit groove 22 along with the extrusion deformation, and the limit block is embedded into the limit groove 22 so that the male die 2 limits the rod 4 to rotate along with the rotation of the female die 3.

The insert 1 is installed at the extrusion working belt 312, the extrusion working belt 312 forms a convex fixture block 3121, in an embodiment, as shown in fig. 4, the number of the fixture blocks 3121 is two, the two fixture blocks 3121 are symmetrically distributed along an axial center line, a clamping groove 11 is formed at a position of the insert 1 corresponding to the fixture block 3121, when the insert 1 is placed into the extrusion working belt 312 from the feeding port 311, the insert 1 is installed at the extrusion working belt 312 through the matching of the clamping groove 11 and the fixture block 3121, the clamping groove 11 and the fixture block 3121 are designed to firmly clamp the insert 1 at the extrusion working belt 312, so that the insert 1 rotates along with the rotation of the die 3, the structure is simple, and the disassembly is convenient. The rod metal passing through the extruded working band, in addition to flowing axially under load, adds to the torsional deformation that occurs in the circumferential direction.

In order to enable the twisting angle to be more inclined and the twisting forming effect to be better, a plurality of inclined grooves 12 are uniformly distributed on the insert 1 along the circumferential direction, as shown in fig. 6, the inclined grooves 12 are grooves which deflect around the central axis of the insert 1, and the inclined grooves 12 can enhance the forming effect when the insert is twisted and extruded simultaneously.

In one embodiment, the ejection mechanism is located in a cavity remote from the inlet.

A method for extrusion molding of a magnesium alloy rod free of anisotropy, as shown in fig. 10, comprising the steps of:

(1) preparation before forming: heating the rod 4 to a forming temperature and rounding off; the male die 2 after preheating and heat preservation is arranged on a press machine, the female die 3 is arranged on a rotating mechanism, and the insert 1 is placed into the extrusion working belt 312 from a feeding port 311 of the cavity 31 and is arranged; uniformly coating oil-based graphite lubricant on the surfaces of the male die 2, the female die 3 and the insert 1 which are to be in contact with the bar 4, and then placing the preheated bar 4 into the cavity 31 from the feeding port 311 of the female die 3;

(2) and (3) starting forming: firstly, a press machine drives a male die 2 to axially feed, a bar 4 is axially pushed to the position of an extrusion working belt 312 to be contacted with an insert 1, then when the bar 4 flows into a chute 12 and is fully filled, a rotating mechanism rotates to drive a female die 3 to rotate, and then the female die 3 drives the insert 1 to rotate, so that the bar 4 at the position of the extrusion working belt 312 is twisted; finally, the male die 2 continues to drive the bar 4 to feed, and the effects of simultaneous twisting and simultaneous extrusion are achieved under the combined action of the insert 1 and the male die 2 until the bar 4 is formed into a formed piece; in the extrusion process, the circumferential torque is provided by the rotation of the female die 3, so that the friction force is greatly reduced, the axial extrusion force is greatly reduced, the material utilization rate is improved, the uniform flow of the bar 4 is promoted, the forming uniformity is improved, the extrusion deformation texture is eliminated, the difference between the axial performance and the circumferential performance of a formed part is greatly reduced, and the forming performance is improved; the large plastic deformation process of twisting and extruding is beneficial to improving the mechanical property of the formed workpiece.

(3) Discharging: and stopping the axial movement of the press, driving the press to move in the reverse axial direction, driving the male die 2 to withdraw from the female die 3 and separate from the formed piece, and finally ejecting the formed piece by an ejection mechanism (not shown in the figure) to finish discharging.

The invention applies torque on the basis of traditional extrusion, can increase the revolution number of rotation by changing the speed of rotation, improves the gradient tissue generated under the rotation forming and realizes the uniform deformation of the tissue. The invention designs the part of the extrusion working belt 312 of the female die 3 into the structure form of the insert 1. On one hand, the insert at the working belt part can be replaced in time after being worn, so that the cost increase caused by the scrapping of the female die 3 is avoided, the service life of the die is prolonged, and the economic benefit is remarkable when the insert is popularized in the forging industry; on the other hand, the extrusion working belt and the insert can be serialized, and formed parts with different extrusion ratios can be obtained by replacing different inserts 1. In the forming process, the female die 3 rotates, generates larger shear strain by changing the internal stress strain state of the deformable body, can refine crystal grains, forms a fine crystal structure with large-angle crystal boundaries, ensures the uniform structure of an extruded piece, and reduces the anisotropy of the formed piece.

The foregoing shows and describes the general principles and features of the present invention, together with the advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims

1. An extrusion forming die of a magnesium alloy rod without anisotropy is characterized in that: the automatic feeding device comprises an insert, a male die connected with a press machine and a female die connected with a rotating mechanism, wherein the male die is connected with the press machine to perform axial motion, the female die is connected with the rotating mechanism to perform circumferential rotation motion, a die cavity is arranged in the female die, the die cavity is provided with a feeding port, an extrusion working belt is further arranged in the die cavity, the feeding port is used for placing the insert, a bar and the male die, and the insert is arranged at the extrusion working belt.

2. The die for extrusion molding of a magnesium alloy rod free of anisotropy according to claim 1, characterized in that: the end of the male die is provided with a punch, the punch is placed into the punch from the feeding port and extrudes the bar, the bottom surface of the punch is provided with a limiting groove, the end surface of the bar, which is contacted with the bottom surface of the punch, generates a limiting block matched with the shape of the limiting groove along with the extrusion deformation, and the bar is limited by the male die to rotate along with the rotation of the female die by embedding the limiting block into the limiting groove.

3. The die for extrusion molding of a magnesium alloy rod free of anisotropy according to claim 1, characterized in that: the extrusion working belt is provided with a clamping block, the insert is provided with a clamping groove at a position corresponding to the clamping block, and when the insert is placed into the extrusion working belt from the feeding port, the insert is arranged at the extrusion working belt through the matching of the clamping groove and the clamping block.

4. The die for extrusion molding of a magnesium alloy rod free of anisotropy according to claim 1, characterized in that: the insert is uniformly distributed with a plurality of chutes along the circumferential direction, and the chutes are grooves which deflect around the central axis of the insert.

5. The die for extrusion molding of a magnesium alloy rod free of anisotropy according to claim 1, characterized in that: the die also comprises an ejection mechanism for discharging the formed bar stock.